Method for adjusting the position of the angle of rotation of the camshaft of a reciprocating piston internal combustion engine in relation to the crankshaft

Abstract: In a method for setting the rotary-angle position of the camshaft of a reciprocating piston internal combustion engine relative to the crankshaft, in which the crankshaft has a drive connection to the camshaft via an adjusting gear which is embodied as a triple shaft gear with a drive shaft which is fixed to the crankshaft, an output shaft which is fixed to the camshaft and an adjusting shaft, a phase angle signal for the rotary-angle position of the camshaft relative to the crankshaft is registered. Travel up to a stop is carried out, during which a stop element which is connected to the drive shaft is moved towards a counterstop element which is connected to the camshaft, while the adoption of a stop position is monitored. When the stop position is detected, a stop phase angle value is determined. The phase angle signal is adjusted to a setpoint phase angle signal which is made available. The stop phase angle value is assigned an adjacent or neighbouring phase angle range and the phase angle signal is compared with the phase angle range. If the setpoint phase angle signal lies within the phase angle range, the adjustment of the phase angle signal to the setpoint phase angle signal is interrupted in order to implement further travel up to a stop. For this purpose, the stop element is moved towards the counterstop element while the adoption of the stop position is monitored. When the stop position is detected, the stop phase angle value is determined again and the adjustment of the phase angle signal to the setpoint phase angle signal is then continued. (end of abstract)

Agent: Lucas & Mercanti, LLP - New York, NY, US
Inventors: Minh Nam Nguyen, Holger Stork, Heiko Dell
USPTO Applicaton #: #20070245989 - Class: 123090170 (USPTO)
Related Patent Categories: Internal-combustion Engines, Poppet Valve Operating Mechanism, With Means For Varying Timing, Camshaft Or Cam Characteristics

Method for adjusting the position of the angle of rotation of the camshaft of a reciprocating piston internal combustion engine in relation to the crankshaft description/claims

The Patent Description & Claims data below is from USPTO Patent Application 20070245989, Method for adjusting the position of the angle of rotation of the camshaft of a reciprocating piston internal combustion engine in relation to the crankshaft.

Brief Patent Description - Full Patent Description - Patent Application Claims

[0001] The invention relates to a method for setting the rotary-angle position of the camshaft of a reciprocating piston internal combustion engine relative to the crankshaft, wherein the crankshaft has a drive connection to the camshaft via an adjusting gear which is embodied as a triple shaft gear with a drive shaft which is fixed to the crankshaft, an output shaft which is fixed to the camshaft and an adjusting shaft, wherein a phase angle signal for the rotary-angle position of the camshaft relative to the crankshaft is registered, wherein travel up to a stop is carried out in which a stop element which is connected to the drive shaft is moved towards a counterstop element which is connected to the camshaft, while the adoption of a stop position is monitored, wherein, when the stop position is detected, a stop phase angle value is determined, and wherein a setpoint phase angle signal is made available and the phase angle signal is adjusted to the setpoint phase angle signal.

[0002] Such a method is known from the practice. In said method the rotary-angle position of the camshaft relative to the crankshaft is adjusted using an electric motor which drives an adjusting shaft of a triple shaft gear which is arranged between the crankshaft and the camshaft. A camshaft gearwheel, which is driven via a chain by a crankshaft gearwheel which is connected in a rotationally fixed fashion to the crankshaft, is provided on the drive shaft of the triple shaft gear. The output shaft of the triple shaft gear is connected in a rotationally fixed fashion to the camshaft. In order to adjust the rotary position or phase angle of the camshaft relative to the crankshaft to a setpoint phase angle signal which is made available, the phase angle is measured and compared with the setpoint value signal. When a deviation occurs, the electric motor is actuated in such a way that the deviation is reduced. So that even in the event of a fault in the adjustment device the functioning of the motor can be maintained, the relative adjustment is limited to a maximum adjustment angle using a stop element which is connected to the drive shaft and interacts with a counterstop element which is fixed to the camshaft.

[0003] Since the location of the stop position is not yet known when the internal combustion engine starts, travel up to a stop is carried out during the starting process of the internal combustion engine, during which travel the stop element is moved, by correspondingly rotating the adjusting shaft, towards the counterstop element until the stop element comes to bear against the counterstop element. In the process, the adoption of the stop position is monitored by sensors. As soon as it is detected that the stop element is positioned against the counterstop element, a phase angle value is assigned to the stop position. This may be done, for example, in such a way that the phase angle signal at the stop position is read out and the corresponding measured value is used as a phase angle value for the stop position. However, there is also the possibility of setting the phase angle signal to zero when the stop position has been reached. In this case, the stop position forms the reference point for the phase angle signal.

[0004] The setpoint phase angle signal is made available by an engine control device which controls the reciprocating piston internal combustion engine. The setpoint phase angle signal is selected as a function of the operating state of the internal combustion engine in such a way that the reciprocating piston internal combustion engine has favourable fuel consumption and low emission of pollutants. The phase angle signal is adjusted to this setpoint phase angle signal in that, when a deviation occurs between the phase angle signal and the setpoint phase angle signal, the adjusting shaft is rotated in such a way that the deviation is reduced. The setpoint phase angle signal is limited as a function of the stop phase angle value in such a way that a collision between the stop element and the counterstop element is avoided during normal operation of the internal combustion engine. However in practice it has become apparent that the stop position can change during the operation of the reciprocating piston internal combustion engine so that said position then no longer corresponds to the stop phase angle value determined during the starting process. In order, nevertheless, to avoid a collision between the stop element and the counterstop element, and thus to avoid the risk of damage to the corresponding parts, in the operating states which occur during normal operation, it is necessary, when limiting the phase angle, to maintain a certain safety interval from the stop phase angle value, as a result of which the adjustment range which is available for setting the phase angle cannot be used completely.

[0005] The object is therefore to provide a method of the type mentioned at the beginning which makes it possible to adapt the stop phase angle value to changes in the operating state of the internal combustion engine.

[0006] This object is achieved by virtue of the fact that the stop phase angle value is assigned an adjacent or neighbouring phase angle range and the phase angle signal is compared with the phase angle range, and in that if the setpoint phase angle signal is within the phase angle range, the adjustment of the phase angle signal to the setpoint phase angle signal is interrupted and further travel up to a stop is carried out during which the stop element is moved towards the counterstop element while the adoption of the stop position is monitored, in that, when the stop position is detected, the stop phase angle value is determined again, and in that the adjustment of the phase angle signal to the setpoint phase angle signal is then continued.

[0007] It is thus advantageously possible, during normal operation of the reciprocating piston internal combustion engine, to determine the stop phase angle value again in order, for example, to adapt it to changed operating conditions of the internal combustion engine. In this context, the travel up to a stop is implemented if the setpoint phase angle signal is located in the vicinity of a stop phase angle value which was determined at an earlier time, for example during the last travel up to a stop so that during the travel up to a stop only a relatively small deviation of the phase angle signal from the setpoint phase angle signal occurs and the travel up to a stop thus has virtually no effect on the fuel consumption, the emission of pollutants or the other operating behaviour of the reciprocating piston internal combustion engine. The travel up to a stop is therefore implemented without the user of the internal combustion engine being aware of it. The stop phase angle value can be used as a reference point for the phase angle signal and/or to limit the phase angle while the phase angle signal is being adjusted.

[0008] In one advantageous embodiment of the invention, the setpoint phase angle signal is compared with the phase angle range during the travel up to a stop, wherein, if the setpoint phase angle signal leaves the phase angle range, the travel up to a stop is aborted and the adjustment of the phase angle signal to the setpoint phase angle signal is resumed. If a deviation between the setpoint phase angle signal and the phase angle range occurs, this deviation is therefore immediately compensated by resuming the phase angle adjustment. In this context, aborting of the travel up to a stop is allowed for. This can then be recovered, if appropriate, at a later time when the setpoint phase angle signal is within the phase angle range again.

[0009] In one expedient refinement of the invention, the time which has passed since the last travel up to a stop is measured and compared with a predefined minimum time period, wherein the implementation of further travel up to a stop is suppressed as long as the minimum time period has not yet been reached. It is assumed in this context that no significant change in the stop position is to be expected within the minimum time period. Unnecessary travel up to a stop is therefore avoided.

[0010] It is particularly advantageous if at least one operating state variable of the internal combustion engine, in particular its operating temperature and/or crankshaft rotational speed is registered, if travel up to a stop is implemented in different operating states, if the stop phase angle values which are respectively determined for the individual operating states are stored in a data memory, and if a stop phase angle value is then determined for an operating state by reading out a stop phase angle value from the data memory as a function of the at least one operating state variable and using it to limit the phase angle signal and/or setpoint phase angle signal and/or as a reference point for the phase angle signal. A characteristic diagram is therefore learnt which can have, for example, as parameters, the cooling water temperature and/or oil temperature of the internal combustion engine and/or the rotational speed of the crankshaft. By using the stop phase angle values which are learnt in this way it is possible to adapt the stop phase angle value in a simple way to a change in the operating state of the internal combustion engine without travel up to a stop having to be carried out again for this purpose. The characteristic diagram is expediently stored in a nonvolatile data memory such as, for example, an EEProm so that it is still available after the internal combustion engine restarts. When the internal combustion engine is first put into operation, the data memory can have previously stored standard values.

[0011] In one preferred embodiment of the invention, the difference between the phase angle signal and the stop phase angle value is determined, with the setpoint phase speed signal being changed as a function of the difference, and in particular being reduced when the difference decreases. As a result, wear on the stop element and the counterstop element is very largely avoided during the travel up to a stop. Nevertheless, the stop position can be found quickly.

[0012] In order to protect the stop element and counterstop element against damage it is possible to limit the rotational speed of the adjusting shaft during the travel up to a stop. This measure is possible particularly if the phase angle is within a predefined surrounding area of the stop phase angle value.

[0013] An electric motor is preferably provided for driving the adjusting shaft, wherein the operating current and/or the operating voltage of the electric motor are limited during the travel up to a stop. This measure also allows damage to the stop element and/or counterstop element to be avoided. The operating current and/or the operating voltage of the electric motor can be limited by pulse width modulation.

[0014] An exemplary embodiment of the invention will be explained in more detail below with reference to the drawing, in which:

[0015] FIG. 1 is a schematic partial illustration of a reciprocating piston internal combustion engine which has a device for setting the phase angle of the camshaft relative to the crankshaft,

[0016] FIG. 2 is a camshaft adjusting device,

[0017] FIG. 3 is a graphic illustration of a phase angle signal and of a setpoint phase angle signal during travel up to a stop, wherein the time is plotted in seconds on the abscissa and the signal amplitude on the ordinate, and

[0018] FIG. 4 is an illustration similar to FIG. 3 but here the travel up to a stop is aborted prematurely.

[0019] An adjusting device for the rotary-angle position of the camshaft 3 relative to the crankshaft 5 of a reciprocating piston internal combustion engine has, according to FIG. 1, an adjusting gear 1 which is embodied as a triple shaft gear with a driveshaft which is fixed to the crankshaft, an output shaft which is fixed to the camshaft and an adjusting shift. The adjusting gear can be an epicyclic gear, preferably a planetary gear.

[0020] The drive shaft is connected in a rotationally fixed fashion to a camshaft gearwheel 2 which has a drive connection in a fashion known per se via a chain or a toothed belt to a crankshaft gearwheel which is arranged in a rotationally fixed fashion on the crankshaft 5 of the internal combustion engine. The output shaft is connected in a rotationally fixed fashion to the camshaft 3. The adjusting shaft is connected in a rotationally fixed fashion to the rotor of an electric motor 4. The adjusting gear 1 is integrated in the hub of the camshaft gearwheel 2.

[0021] So that the rotational angle between the camshaft 3 and the crankshaft 5 is limited in the case of a fault in the actuation of the electric motor 4 and a collision 9 between the valves and the reciprocating pistons is reliably avoided, the adjusting device has a stop element 6, permanently connected to the drive shaft of the adjusting gear 1, and a counterstop element 7 which is connected to the camshaft 3 in a rotationally fixed fashion and comes to bear against the stop element 4 in a stop position in the position of use.

[0022] FIG. 1 shows that, in order to measure the crankshaft rotational angle, a magnetic detector 8 is provided which detects the tooth edges of Y a crown gear 9 which is composed of a magnetically permeable material and is arranged on the crankshaft 5. One of the tooth gaps or teeth of the crown gear 9 has a larger width than the other tooth gaps or teeth and marks a reference rotary-angle position of the crankshaft 5.

[0023] When the reference rotary-angle position is reached, a reference mark is generated in the sensor signal of the magnetic detector 8, which is also referred to below as crankshaft sensor signal. This is achieved by virtue of the fact that the crankshaft crown gear 9 has a larger gap at the reference rotary-angle position than between its other teeth. As soon as the reference mark in the crankshaft sensor signal is detected, a rotary-angle measurement signal is set to a value assigned to the reference rotary-angle position. The rotary-angle measurement signal is then correspondingly adjusted whenever there is a change in the state of the crankshaft sensor signal by virtue of the fact that an interrupt is triggered in an operating program of the control unit and the rotary-angle measurement signal is incremented in said interrupt.

[0024] An EC motor which has a rotor on whose circumference is arranged a row of magnet segments which interact magnetically via an airgap with teeth of a stator and which are magnetized alternately in opposite directions with respect to one another is provided as the electric motor 4. The teeth are would with a winding which is energized via an actuation device.

Brief Patent Description - Full Patent Description - Patent Application Claims
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